Remote-control system



June 18,' 1946.

T. W. HAYs REMOTE CONTROL SYSTEM v Filed June 15, 1944 .inn

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bx b fIJIL* lrvvmml SNN Patented June 18, 1946 UNITED STATES mmm-OFFICE Thomas W. HaysLlSalt Lake City, Utah',` assignor ytod'llie Union Switch and Signal Company, Swissvale, Pa., a corporation of .Pennsylvania Application June 15, 1944, serial No. 540,445

4 claims. (177-353). l

My invention relates to remote control Systems, and more particularly to code communication systems for use in centralized traffic control systems for railroads and to the line circuits for such systms; i v

The object of my invention is to provide imL proved means fo'r indicating the occurrence of faults in the line circuits emp-loyed by code com,- muriicatio'n systems by the operation of Va bell or lamp signal at the'control ofilce in response to a cross or short circuit between the line wires, so that the occurrence of such a fault maybe quickly brought to the attention of the operator in "charge,

In the application of a lcode communication system to a large installation as, for example, one covering an entire engine division carrying heavy traic, the number of codes to. be transmitted may exceed the' capacity of the apparatus.- Under these ci-rciimstances it is the practice to divide the line into sections by electrical lter's' "at one or more points, each section providing a battery line'circitfor the control of coding' nit's at the usual n'ur'nber of way stations within the capacity of a set of coding' apparatus and to repeat the c'des transmitted between the control cnice and those stations located in the sections remote from the oflice over the line wires o'f the intervening sections by means of superimposed carrier `urrents of different frequencies By this means a very large number 'of stations may be controlled over the san-1e pair of line wires.

My invention is particularly advantageous for use" in large installations 'of this character which ifi'clde reinote lin'e' circuits, the condition of is not directly observable at the control .I

I shall describe one form of apparatus embodying" invention Aand shall then point out the ov'elfeatiires' thereof in claiins'.

Referring to the accompanying drawing," the reference characters YI and ZI designate a pair of line wires' which are connected through a suitable high pass iter network- HPF with a second pair oiliii wires' YZA and Z2 to form a through lin circuit extending from a ontioloilice, 'shown at the left, through a plurality of way stations at each of which a coding unit is provided 'for coniiifinication with theA control cnice.v To show the application of the fault detecting apparatus of Iny invention to a specific communication system; I have illustrated it lierein as applied to the r'einte control system of Letters Patent of the United States No; 2,303,875, is'siIed December l, 1,942, to George W. Baiigliman and Norman F. Agnew; and I have ssuld that a Set Of the coding apparatus shown in this patent is arranged tov control a group of stations located in the territory over'which the line wires Yi` and ZI extend, and that a second set of similar coding apparatus is arranged to control a second group of stations located in the territory over which the line Wires YZ and Z2 extend. The codes for this section Yare repeated over the line wires of the first secjtion by means of carrier currents in the manner disclosed in a pending application for Letters -Patent of the United States forY Remote control systems; Serial No. 455,577,` led August2 1, 1942, by thesame inventors, now Patent No. 2,350-668, issued June 6i 1942i. In accordance with'` this arrangement a line battery 8i! is provided for `'each line section by means of which the line relays R at the stations in the corresponding line sect-ion are normally energized, and the line relays andibattery are connected across the fline wires in 'multipla with a low pass filter network LPFinterposed in each line connection. Eachline section remote from the oil'lce is provided with a remote line unit or repeater as indicated on the drawing which is generally similar to the one shown in the application referred to, but with the addition of a short circuit detector relay LSR in series in the connection of the line battery 30 to the line wires in accordance with my invention.

It is to be understood that the control ofce is provided with a, separate coding unit for each line section 'each including the usual transmitting and receiving relays. y

The normal mode of operation of the remote control system is as follows: Control codes are transmitted to the stations lin each section by the periodic operation of the transmitter relay of the corresponding oiilce coding unit.- In the case of the 'first section, comprising line wires YI and the 'transmitter relay interrupts the line vcircuit directly, as described in the patent, while in the case of each remote section such as the one comprising the line wires Y2 and Z2 the line circuit lis interrupted by the operation of Aa control relay CR which is a repeater of rthe transmitter relay of the corresponding oice coding unit and is controlledby carrier current of a distinctive frequency transmitted over the line wires of the intervening section or sections. The station line relays R which respond to the codes are of the biased polar type andv assume their energized positions in which their left-hand contacts are closed, onlywhen supplied withr current of tlie` polarity normally supplied to their line cicuitby the corresponding battery 8i).4

Each station coding unit includes a master relay M and a transmitter relay T, by means of which indication codes are delivered to the line circuit by connecting the line wires together periodically over contact b of relay T.

Arrangements for preventing interference are provided, as described in the patent but not shown herein, whereby a station can initiate the transmission of an indication code only when the line is free, and in the event two or more codes are initiated at the same time they are transmitted but one at a time in a given order.

The remote line unit as shown herein includes a receiving relay IR of the stick polar type inductively coupled to the line circuit through an impulse transformer 4U and thereby rendered responsive to the line current Variations produced by the periodic operation of a station transmitter relay T, and also includes a group of slow acting relays PC, PCP, LI and L2 for governing its operation. Y

When a control code of carrier current impulses is received by the remote line unit, relay PCP is picked up in response to the iirst operation of relay CR, over a circuit extending from the positive terminal B of a suitable local source of current at the left-hand contact a of relay CR which extends through the winding of relay PCP to the negative terminal C of the same source. Relay PCP therefore picks up at the beginning of a control code, and is made suiciently slow in releasing so that it remains picked Y up until after the code operation of relay CR ceases. Relay PC remains released holding relay L2 energized and relay LI, which is slow to release, remains picked up although its circuit is opened intermittently by relay CR. Relay IR remains in its normal position as shown because its upper winding and the secondary winding of transformer 4|lare short circuited over front contact c of relay PCP, and the lower winding of relay IR is energized in a direction to hold r relay IR normal over the circuit including front contact rb of relay PCP. Relay IR therefore does not respond to a control code.

To initiate an indication code relays M and T pick up at the transmitting station, relay M remaining energized and relay T operating periodically in accordance with the code. At the beginning of the code, the associated line relay R lreleases due to the reversal of its connections by contacts :i and 7c of relay M, and the closing of contact b of relay T connects the line wires together through the coils of the associated iilter LPF, thereby short circuiting the associated relay R and causing the line current to increase to reverse relay IR of the remote line unit, whereupon relay PC becomes energized over a circuit extending from terminal B over the right-hand contacts a of relays CR and IR through relay PC to terminal C at contact a of relay LI. Relay PC completes a stick circuit at its own front contact a extending to terminal B at contact a voli relay CR whereby it is held energized inde'- pendently of relay IR, relay LI remaining picked up provided relay IR responds to the code so as to periodically close the circuit for relay LI. By closing its front contact e, relay PC energizes relay PCP, and contacts b and d of relay PC reverse the polarity of the line current to release the line relays at stations other than the one which is transmitting the code. Relay IR is held reversed locally during the change in the line polarity over a circuit including its middle winding and front contact f of relay PC, and transformer 40 is momentarily short circuited at the same time over front contact c of relay PC. Relay L2 then releases in response to the opening of back contacts e of relays PC and PCP, and contacts a and c of relay L2 operate to render relay CR incapable of interrupting the line circuit during the transmission of the indication code by relay T. Relay IR follows the code, being operated to the right when relay T releases and to the left when relay T picks up, and controls a C. C. oscillator whereby the code is repeated over line wires YI and ZI as carrier current impulses of a distinctive frequency to operate the corresponding receiving relay at the oilice. Y

The o'ice apparatus as described in the above mentioned application Serial No. 455,577 transmits a single impulse to operate relay CR momentarily following the reception of a complete code. This operation releases relay PC, but without interrupting the line circuit including the line wires Y2 and Z2 because the impulse is received after relay L2 is released. The release of relay PC restores the line polarity to normal and while the line polarity is being changed relay IR is held normal over a local circuit including its lower winding and back contact f of relay PC. Transformer 40 is momentarily short circuited at the same time'over backcontact c of relay PC. Relay PCP then releases and relay L2 becomes reenergized, and at the transmitting station, relay M releases to render the associated relay R responsive to the current of normal polarity which is now supplied to the line, the relays R at other stations controlled over line `wiresY2 and Z2 also becoming energized at this time.

It may happen that when the system is in its normal at rest condition, relay IR will become reversed due to a fault such as a short circuit between line wires Y2 and Z2. In this case relay IR will remain reversed for a time longer than occurs in normal operation causing relays PC and PCP to pick up and relay L2 to release as above described but causing relay LI to release also, whereupon relay PC will release thereby restoring relay IR to normal and causing relay PCP to release and relays LlV and' L2 to become reenergized. i

The oce coding unit may be arranged to cause relay CR to be operated momentarily to release relay PC when the code operation of relay IR ceases, even though the code is not complete, and -s so described in the application Serial No. 455,577 hereinbefore referred to. It follows that relay PC would be released by relay CR in the event of a fault, if relay LI were not provided. The provision of relay LI is however desirable because it causes the remote line unit to be self-restoring in the event of a fault, independently of the condition of the apparatus at the control office.

Considering now the fault detecting apparatus of my invention, this includes a fault relay'LSR connected in series with the line battery 80, a relay similar to relay LSR being providedvfor each line circuit. The line winding of relay LSR is shunted by an adjustable resistor 5 which is adjusted to cause the relay to pick up in response to a relatively small increase in the line current, so that relay LSR normally remains released and responds when the line Wires are connected together at any point due to a fault. The fault relay LSR is slow to pick up and quick to release due to its limited degree of energization and to the provision of a short circuited winding as shown, in addition to the shunt resistance 5, and

when the line current yis 'increased due to the shunt fappliedby a transmitter relay T, relay reverses and'relay PC 'picks up 'before -relay LSR has had time lto 'assume its energized position. The closing of front contact g lof relay PC short circuits the line winding of relay LSR, and it normal period, relays Li and PC will release asY already pointed out, and the opening of contact g of relay PC will cause relay LSR to pick up if the line current is above normal, indicating a fault. Relay LSR does not respond during the transmission of control codes, vin which case the line current is not increased, and consequently responds selectively to line faults which persist for a time measured by relays L! and PC.

When relay LSR becomes energized, the fact is made manifest to the operator by the energization of an indication relay K at the oice which repeats the operation of relay LSR and which when energized lights a suitable lamp G. Relay K may be controlled over any available communication channel extending between the location of the remote line unit and the office, this for simplicity being indicated herein as a direct wire connection including contact a of relay LSR. In practice, however, it is usually preferable to use one of the indication channels provided byy the adjacent station coding unit ofthat set of coding apparatus for which the next section of the line in the direction of the oilce provides a vphysical line circuit, such as the one connected to line wires Y! and ZI for example, as will be readily understood by reference to the analogous arrangements for indicating the condition of a4 change-over relay associated with the remote line unit as illustrated in application Serial No. 455,577 hereinbefore referred to. The fault relay LSR for the rst line section will of course be locatedr at the omce, and will control a lamp E directly.

Since relay LSR is adjusted to pick up in response to a relatively small increase in line current, a reduction of the line current to normal upon the removal of the fault may be insuflcient to cause it to release. This is desirable as it makes it more certain that the operator will observe the lighting of lamp E due to a. temporary fault, and presents no difficulty because relay LSR will release in response to the rst line open period of the next control code transmitted by the operator.

In the above-mentioned Patent No. 2,303,875 it is pointed out that although a shunt applied to the line near the battery end will release all of the line relays, it may be that those near the battery end will not release when the shunt is applied near the distant end, for the reason that such a shunt is relatively ineilective, due to the resistance of the intervening line wire included therein. These line relays will release temporarily due to the operation of relay PC in the case of a fault but may pick up again when relay PC is released. In this case the system remains operative with respect to nearby stations, even though relay LSR remains energized due to a fault near the far end of the line. By sending a control code to each station in turn under this condition to cause each station remaining operative to send an indication code, the operator 6 'isA able to determine vthe app'roxiinate location 'of 'the fault.

`Although I have herein shown and described ronly one forni of apparatus embodying my invention, it is understood that various changes and modifications may Vbe made therein within the scope of the appended claims without departing from the 'spirit 'and scope -of my invention.

`-I-'Iaving thus 'described my invention, what I claim is: l. In a 'remote control system, a normally 'energizedlinecircuit including a source of current two line wires in which current of a given value normally flows, a code transmitter adapted `to periodically connect said line wires together so as to increasethe current supplied to said line circuit and thereby deliver codes of current variations thereto, a polarizedV relay inductively coupled to said line circuit between said source and said line wires and operable between a normal and a reverse position in response to each such current variation, a fault relay interposed in said circuit between said source and said line wires and adapted to assume its energized position when said line wires remain connected together so as to increase the current supplied thereto for a predetermined time, a slow acting relay energized by the polar relay in its normal position and having a release period which exceeds the time the polar relay remains in its reversed position during a code, a stick relay controlled by said slow acting relay and by said polar relay, means for energizing said stick relay upon the reversal of said polar relay, means for maintaining said stick relay energized until a complete code is delivered by said code transmitter or until said slow acting relay releases, means controlled by said stick relay when energized for preventing the energization of said fault relay when the line wires are connected together temporarily due to the operation of said code transmitter, and indication means controlled by said fault relay for indicating when said fault relay is operated.

2. In a remote control system, a normally energized line circuit including a source of current and two line wires in which current of a given value normally flows, a code transmitter adapted to periodically connect said line Wires together so as to increase the current in said line circuit and thereby deliver codes of current variations thereto, a quick acting line relay responsive to variations in the current delivered to the line wires by said source for receiving said codes, a slow acting fault relay interposed in said line circuit between said source and said line wires and adapted to assume its energized position when the line wires are connected together so as to increase the current in said line circuit, a quick acting stick relay which becomes energized whenever the line relay responds to an increase in line current and which releases at the end of a complete code, a slow acting relay which is energized whenever the line relay responds to a decrease in the line current to its normal value, means controlled by said stick relay when energized for rendering said fault relay non-responsive to the current in said line circuit, and means including said slow acting relay for maintaining said stick relay energized dependent upon the periodic operation of said line relay, thereby maintaining said fault relay non-responsive during the operation of said code transmitter and rendering said relay selectively responsive to a short circuit between said line Wires.

3. In a remote control system, a normally en- -ergized line circuit including a source of current and two line wires in which current of a given value normally flows, a code transmitter adapted to periodically connect said line Wires together so as to increase the current in said line circuit and thereby deliver-codes of current variations thereto, 1a slow acting fault relay and a quick acting line relay each of which is responsive to an increase in the current normally delivered to said line circuit by said source, a stick relay,vmeans controlled by said stick relay when energized for preventing the operation of said fault relay, means controlled by said line -relay when operated in response to an increase in line current for energizing said-stick relay, and timing means controlled by said line relay for releasing said stick relay iny the event said increase in line current persists for. a predetermined time interval which is longer than any interval during which said line wires are connected together due to the operation of said code transmitter.

4. In a remotecontrol system. a normally energized line circuit including a source of current and two line Wires in which current of a given value normally ows, a code transmitter adapted to periodically connect said line wires together so as to increase the current insaid line circuit and thereby deliver codes of current variations thereto, a fault relay interposed in the connection of said source to the line wires and arranged to pick up selectively in response to an increase in line current which persists for a predetermined time greater than any interval said line Wires are connected together during the operation of said code transmitter and to remain picked up if the line current is subsequently decreased to its normal value, indication means at a distant. control ofce for indicating when said fault relay is energized, and means remotely controlled from said oiice for momentarily opening said line circuit to release said fault relay.

THOMAS W. HAYS. 

